In a general sense, the present invention relates to a holder for a portable electronic device. More specifically, the invention has been devised in the context of a so-called deskstand for a radio telephone handset and a battery pack therefor.
A common accessory for a radio telephone handset is a deskstand. A deskstand is designed to serve any one or all of a number functions: It primarily holds the handset or battery pack, usually in an upstanding position, for example simply for storage. It can have electrical connectors for delivering electrical current for recharging a battery pack, the battery pack being either connected to or detached from the handset. It may also provide electronic communication links to and from the radio telephone handset, for example for effecting data transfer.
A deskstand typically consists of a body having a flat base for sitting on a desk top and one or more recesses, or slots, provided in the body for receiving a handset and/or a battery pack. The recesses are dimensioned such that when a handset or battery pack is in situ, the lower region of the handset/battery pack is cradled by the deskstand and the handset/battery pack extends substantially vertically. In the case of a handset, respective sets of electrical connectors, for example in the form of contact pads, or male/female interface connectors, are provided between the handset and the deskstand to effect data transfer to and from an inserted handset; in the case of a battery pack, spring loaded connectors are provided for power charge-up. The typical deskstand, relies on the combination of the frictional fit between the outer surfaces of the handset/battery pack and the walls of the deskstand forming the recess, and gravitational forces acting on the handset/battery (i.e. its weight) to retain the handset/battery in place in the deskstand thereby maintaining the requisite electrical connections.
Certain shortcomings with this way of retaining a handset/battery pack in situ in the deskstand are becoming apparent. With the trend continuing towards ever smaller and lighter handsets--and hence battery packs--the weight of the handset/battery pack in itself is proving to be insufficient for retaining the handset/battery pack in satisfactory electrical communication with the deskstand. This problem is becoming more acute as handsets are being equipped with wide-ranging and complex telecommunication facilities, and the number of data transfer pins is expanding.
One attempt to solve this problem has been to use electrical connectors having relatively high contact spring forces in order to overcome the contact resistance and ensure electrical communication. However, with deskstands becoming smaller along with handsets, there is a limit to the extent of spring contacts that can viably be housed, so this solution is found to be less than satisfactory.
Other solutions have proposed using formations between the deskstand and handset/battery pack to interconnect the two. For example international application published under WO 95/08847 discloses a battery pack retention system for a battery recharging unit consisting of rails provided on opposite side walls of the charger retention area (recess) and corresponding length wise channels formed in the opposite sides of the battery pack. In addition the channels are provided with small compliant `bumps` which when the battery pack is in situ are flexed inwards and so resiliently push outwards against the rails. Apart from the inherent awkwardness of aligning the rails in relation to the channels when inserting a battery pack, the compliant bumps gradually wear away consequently reducing the effective force which they can exert against the rails. More significantly however is that the disclosed retention system is dependent on the weight of the battery pack to induce sufficient frictional contact force to hold it in place in the retention area.